GRE supports many protocols like IP, IPX, AppleTalk, CLNS(ISO).
Steps to enable GRE :
1. Configure gr-0/0/0.0 with tunnel source, destination, MTU and fragmentation
2. Enable ISO to support ISIS protocol
3. Enable ISIS in LAN and GRE interface
root@R1> show configuration interfaces gr-0/0/0.0
clear-dont-fragment-bit;
tunnel {
source 198.51.100.1;
destination 203.0.113.2;
allow-fragmentation;
path-mtu-discovery;
}
family inet {
mtu 1524;
address 192.168.0.1/30;
}
family iso;
root@R1> show configuration protocols isis
interface gr-0/0/0.0;
interface ge-0/0/1.0;
ISIS Adjacency status:
root@R1> show isis adjacency
Interface System L State Hold (secs) SNPA
gr-0/0/0.0 R2 3 Up 25
ISIS routing table:
root@R1> show route protocol isis
inet.0: 8 destinations, 8 routes (8 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
172.23.7.0/24 *[IS-IS/15] 00:35:38, metric 20
> to 192.168.0.2 via gr-0/0/0.0
iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)
We are able to reach remote host from host 1
root@Ubuntu-1:~# ping 172.23.7.2
PING 172.23.7.2 (172.23.7.2) 56(84) bytes of data.
64 bytes from 172.23.7.2: icmp_seq=1 ttl=62 time=3.52 ms
64 bytes from 172.23.7.2: icmp_seq=2 ttl=62 time=3.96 ms
64 bytes from 172.23.7.2: icmp_seq=3 ttl=62 time=2.88 ms
64 bytes from 172.23.7.2: icmp_seq=4 ttl=62 time=3.36 ms
